To the Editor.
—Kroenke et al,1 in their study of hypomagnesemia in diuretictreated patients make the assertion that, because the serum magnesium level in treated patients vs the control group is not significantly different, there is no need for routine measurement of the serum magnesium level. The issue, however, is the reliability of the serum magnesium level in reflecting total body magnesium. Although the authors of this study acknowledge the shortcomings of the serum magnesium level, this did not make them any more cautious about their conclusions. In stable healthy patients, there is a good correlation between serum and bone magnesium levels (0.96), but this is not true in the disease state.2 In the latter situation a combination of tests, ie, serum magnesium and percentage magnesium retention following a test load, is a better indicator of body magnesium status.3 All one has to do is to stop